Table 2.
Experimental conditions (factors and levels of the orthogonal array) and results (COD as value±expanded uncertainty) for tannery wastewater (pH1 = 3.0, pH2 = 9.0, K2FeO4(1) = 0.400 g/L, K2FeO4(2) = 1.200 g/L, time(1) = 3.00 min, time(2) = 9.00 min). The dose of Envifer® was calculated based on pure K2FeO4.
| Run | Experimental Conditions | Experimental Results * | ||||||
|---|---|---|---|---|---|---|---|---|
| Repetition | pH | K2FeO4 | Time | pH | K2FeO4 (g/L) | Time (min) | COD (g O2/L) | |
| 1 | 1 | 1 | 1 | 1 | 3.0 | 0.400 | 3.00 | 7.340 ± 1.100 |
| 2 | 1 | 1 | 2 | 2 | 3.0 | 1.200 | 9.00 | 2.850 ± 0.430 |
| 3 | 1 | 2 | 1 | 2 | 9.0 | 0.400 | 9.00 | 8.570 ± 1.290 |
| 4 | 1 | 2 | 2 | 1 | 9.0 | 1.200 | 3.00 | 8.720 ± 1.310 |
| 5 | 2 | 1 | 1 | 1 | 3.0 | 0.400 | 3.00 | 7.390 ± 1.110 |
| 6 | 2 | 1 | 2 | 2 | 3.0 | 1.200 | 9.00 | 2.790 ± 0.420 |
| 7 | 2 | 2 | 1 | 2 | 9.0 | 0.400 | 9.00 | 8.600 ± 1.290 |
| 8 | 2 | 2 | 2 | 1 | 9.0 | 1.200 | 3.00 | 8.750 ± 1.310 |
| 9 | 3 | 1 | 1 | 1 | 3.0 | 0.400 | 3.00 | 7.340 ± 1.100 |
| 10 | 3 | 1 | 2 | 2 | 3.0 | 1.200 | 9.00 | 2.710 ± 0.410 |
| 11 | 3 | 2 | 1 | 2 | 9.0 | 0.400 | 9.00 | 8.640 ± 1.300 |
| 12 | 3 | 2 | 2 | 1 | 9.0 | 1.200 | 3.00 | 8.730 ± 1.310 |
* parameter value ± the measurement uncertainty for an extension factor k = 2.